GAP insurance simply covers the difference, or gap, between what your bike is worth and what you owe on it. KBB will tell you what your insurance will pay out if your bike is totalled or stolen, so if you owe more than the KBB estimate, that difference is how much your GAP insurance will pay. It is normally worth getting/keeping if you are financing a new vehicle.

I didn't know you could even get GAP insurance without having the vehicle insured, but I am pretty sure they are still only going to pay you the difference between KBB and what you owe. I would get insurance!